Image edge enhancement
= Image edge enhancement
<image edge> enhancement increases the apparent sharpness or contrast of an <image edge>. <Unsharp masking> gives bounded linear high-frequency amplification; backward normal diffusion in the <Perona-Malik equation> gives formal nonlinear sharpening with <ill-posedness> risks. Positive diffusion tensors chiefly preserve or connect structure rather than perform unbounded backward diffusion.